Preparation method and application of reference electrode in small flexible electrochemical device

Abstract

A preparation method and application of a reference electrode in a small flexible electrochemical device, belonging to the field of electrochemistry. The present invention deposits an electrode with a fishbone-shaped silver nanowire structure on a modified Flexdym flexible substrate by an electrochemical deposition method, and then electrochemically chlorinates the electrode to obtain Fishbone‑Ag / AgClRE. The present invention uses Flexdym material as a flexible substrate for the first time, and uses a mixed solution of PAA and Gly for hydrophilic modification of the Flexdym flexible substrate for the first time. The present invention adopts an electrochemical chlorination method, which has better controllability, and the prepared reference electrode has better performance. The present invention prepares a reference electrode with a fishbone-shaped silver nanowire structure for the first time. The reference electrode with this structure has better stability, service life and storage life than the published or commercially available sheet reference electrodes. The reference electrode of the present invention can be applied to electrochemical electrocatalytic reactions and can be easily prepared into a small flexible electrochemical device.

Description

Technical Field

[0001] The invention belongs to the field of electrochemistry, and in particular relates to a preparation method and application of a reference electrode in a small flexible electrochemical device. Background Art

[0002] In recent years, due to the development of miniaturized integrated equipment [1] , people have been committed to studying the preparation of sheet reference electrodes [2] The most widely used preparation method is screen printing. [3] and inkjet printing [4] However, the reference electrodes prepared by these two methods are composed of silver nanoparticles, and the reference electrodes prepared have the following problems: 1. The electrode stability is low and is far behind the commercial hard glass Ag / AgCl reference electrode; 2. The service life of the electrode is very short; 3. The long-term stability of the electrode is very poor, which affects the application of the electrode in real life. [5] A silver nanowire-based reference electrode was fabricated on a PDMS substrate. The researchers found that this combined wire- and bead-like Ag / AgCl nanostructure provided the reference electrode with improved stability and a longer lifespan. However, the stability of this reference electrode still cannot match that of commercial hard-glass Ag / AgCl reference electrodes. Currently, the primary challenge facing sheet reference electrode research is how to improve the electrode's stability to the level of commercial hard-glass Ag / AgCl reference electrodes, while also improving both its lifespan and long-term stability. Summary of the Invention

[0003] To address the shortcomings of existing electrodes, such as low stability, short service life, and poor long-term stability, the present invention discloses a method for preparing a flexible fishbone-shaped Ag / AgCl reference electrode (Fishbone-Ag / AgCl RE) for use in small, flexible electrochemical devices and its application. This electrode offers advantages such as high sensitivity, stable performance, high selectivity, and long service life, and can be used for electrochemical catalysis and detection.

[0004] To achieve the above objectives, the present invention employs the following technical solutions: first, an electrode with a fishbone-shaped silver nanowire structure is deposited on a modified Flexdym flexible substrate by electrochemical deposition, and then the electrode is chlorinated by chronopotentiometry to produce Fishbone-Ag / AgCl RE. The specific steps are as follows:

[0005] Step 1: Prepare thermoplastic elastomer Flexdym material as a flexible substrate;

[0006] Step 2: Soak the Flexdym flexible substrate material in a modification solution to perform surface hydrophilic modification;

[0007] Step 3: Preparation of Fishbone-Ag / AgCl RE;

[0008] Step 3.1: Evenly coat the AgNWs solution on the surface of the Flexdym substrate to obtain an AgNWs electrode;

[0009] Step 3.2: Place the AgNWs electrode prepared in step 3.1 in a mixed solution of AgNO3 and KNO3, and deposit silver using chronopotentiometry to obtain a Fishbone-Ag electrode;

[0010] Step 3.3: Chlorination of the Fishbone-Ag electrode: Using the Fishbone-Ag electrode prepared in step 3.2 as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum electrode as the counter electrode, electrochemical chlorination was performed in HCl solution using chronopotentiometry to obtain a Fishbone-Ag / AgCl reference electrode.

[0011] In the above method, in step 2, the modification solution is a mixture of 1-5% by mass polyacrylic acid (PAA) and 5-10% by mass glycerol (Gly). Preferably, a mixture of 3% by mass PAA and 7% by mass Gly is used. Using a PAA-Gly mixture as the modification solution increases the hydrophilicity of the Flexdym substrate, making it easier to coat the AgNW solution in subsequent steps.

[0012] In the above method, in step 2, the surface hydrophilic modification method is as follows: immersing the Flexdym flexible substrate material in a modification solution consisting of 3% by mass PAA and 7% by mass Gly for 30 minutes, drying it in a vacuum oven at 70°C for 1.5 hours, repeating the 30-minute immersion in the modification solution and 1.5-hour vacuum drying at 70°C, and then heat-fixing it in a vacuum oven at 90°C for 30 minutes. The 30-minute immersion in the modification solution, 1.5-hour vacuum drying at 70°C, and 30-minute vacuum fixing are then repeated.

[0013] In the above method, in step 3.1, the concentration of the AgNWs solution is 1-5 mg / mL, preferably, the concentration of the AgNWs solution is 3 mg / mL.

[0014] In the above method, in step 3.2, the concentration of the AgNO3 solution is 0.01-0.02M, and the concentration of the KNO3 solution is 0.1-0.2M. Preferably, the concentration of the AgNO3 solution is 0.015M, and the concentration of the KNO3 solution is 0.15M.

[0015] In the above method, in step 3.2, silver is deposited using chronopotentiometry, with a deposition current of -0.6 mA and a deposition time of 500 to 2000 s. Preferably, the deposition current is -0.6 mA and the deposition time is 1800 s.

[0016] In the above method, in step 3.3, the concentration of the HCl solution is 0.05-0.15 M, preferably, the concentration of the HCl solution is 0.1 M.

[0017] In the above method, in step 3.3, electrochemical chlorination is performed using chronopotentiometry, the chlorination potential is OCP + 100mV, OCP + 150mV, OCP + 200mV, OCP + 250mV, OCP + 300mV, and the chlorination time is 800s, 1600s, 2400s, 2700s, and 3200s. Preferably, the chlorination potential is OCP + 200mV, and the chlorination time is 2700s.

[0018] The present invention also discloses the application of a Fishbone-Ag / AgCl RE in the electrochemical catalysis and detection of ethanol. Cyclic voltammetry was performed using the prepared Fishbone-Ag / AgCl electrode as a reference electrode to catalyze ethanol. Experimental results showed that the ethanol oxidation peak of the prepared Fishbone-Ag / AgCl electrode was similar to that of a commercial hard glass Ag / AgCl electrode, indicating its application in electrocatalysis.

[0019] The present invention also protects the application of a Fishbone-Ag / AgCl RE in detecting glucose in a small flexible electrochemical device. The sheet-shaped reference electrode provides a possibility for miniaturization and portability of the electrochemical system.

[0020] Beneficial effects: The present invention uses Flexdym material as a flexible substrate for the first time, which has the advantages of short processing time, simple manufacturing process, and fast molding. For the first time, a mixed solution of PAA and Gly is used to hydrophilically modify the Flexdym flexible substrate, which can effectively increase the hydrophilicity of the Flexdym substrate. The present invention adopts an electrochemical chlorination method, which has better controllability and the prepared reference electrode has better performance. The present invention is the first to prepare an electrode with a fishbone-shaped silver nanowire structure. The electrode with this structure has very excellent stability, service life and storage life compared to published or commercially available sheet reference electrodes. The electrode of the present invention can be applied to electrochemical electrocatalytic reactions and can be easily prepared into a small flexible electrochemical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the SEM image of Fishbone-Ag / AgCl RE prepared by chemical chlorination;

[0022] Figure 2 This is the SEM image of Fishbone-Ag / AgCl RE prepared by electrochemical chlorination;

[0023] Figure 3 The OCP results of Fishbone-Ag / AgCl RE prepared by electrochemical chlorination and chemical method;

[0024] Figure 4 OCP curves of Fishbone-Ag / AgCl RE and AgNWs-Ag / AgCl RE prepared under optimal conditions in 3M KCl aqueous solution;

[0025] Figure 5 OCP curves of Fishbone-Ag / AgCl RE and commercial hard glass Ag / AgCl RE in 3M KCl aqueous solution;

[0026] Figure 6 is the storage life of Fishbone-Ag / AgCl RE;

[0027] Figure 7 This is a comparison of the ethanol oxidation peaks catalyzed by Fishbone-Ag / AgCl RE and commercial hard glass Ag / AgCl RE;

[0028] Figure 8 This is a physical picture of a three-electrode integrated device;

[0029] Figure 9 The cyclic voltammogram of the three-electrode integrated device catalyzing 20 mM glucose. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the following examples. Unless otherwise specified, the experimental methods described in the examples are all conventional methods; unless otherwise specified, the experimental reagents and materials described can be obtained from commercial sources.

[0031] Example 1

[0032] A method for preparing a reference electrode Fishbone-Ag / AgCl RE used in small flexible electrochemical devices, comprising the following steps:

[0033] Step 1: Make the thermoplastic elastomer Flexdym material as a flexible substrate

[0034] The Flexdym material used in the present invention was purchased from Zhejiang Yangqing Chip Technology Co., Ltd., with a specification of 20 cm×20 cm and a thickness of 2 mm.

[0035] Cut a piece of Flexdym material into a circular shape the size of a 4-inch silicon wafer and place it between two single-side polished silicon wafers that have been pre-treated with a silanizing agent. Place the wafers in a hot press at 167°C for 6 minutes. Remove the pressed Flexdym film to create a flexible substrate made of thermoplastic elastomer Flexdym material. Cut this flexible substrate into small pieces for later use.

[0036] Step 2: Hydrophilic modification of the Flexdym substrate surface

[0037] Step 2.1: Prepare a mixed aqueous solution of 3% PAA and 7% Gly by mass;

[0038] Step 2.2: Soak the prepared Flexdym flexible substrate in a mixed solution of 3% by mass PAA and 7% by mass Gly for 30 minutes, and then dry it in a vacuum oven at 70°C for 1.5 hours;

[0039] Step 2.3: Repeat step 2.2 once;

[0040] Step 2.4: Place the Flexdym flexible substrate in a vacuum oven at 90°C for 30 minutes.

[0041] Step 2.5: Repeat steps 2.2 and 2.4 once to obtain a Flexdym substrate modified with a surface hydrophilic layer.

[0042] Step 3: Preparation of Fishbone-Ag / AgCl RE

[0043] Step 3.1: Prepare the AgNWs electrode by evenly coating 3 mg / mL of AgNWs on the surface of the Flexdym substrate and leaving it at room temperature for 1 day to obtain the AgNWs electrode;

[0044] Step 3.2: Place the AgNWs electrode prepared in step 3.1 in a mixed solution of 0.015M AgNO3 and 0.15M KNO3 and deposit silver using chronopotentiometry at a deposition current of -0.6 mA for 1800 s. The deposited electrode has silver branches with fishbone-like nanostructures. Protect the electrode with N2 and set aside for future use.

[0045] Step 3.3: Chlorination of Fishbone-Ag: Using the Fishbone-Ag electrode prepared in step 3.2 as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum electrode as the counter electrode, chlorination was performed using chronopotentiometry in a 0.1 M HCl solution. The chlorination potential was OCP + 200 mV and the chlorination time was 2700 s to prepare Fishbone-Ag / AgCl RE. The product was then washed three times with deionized water, dried with N2, and stored at room temperature away from light.

[0046] Comparative Example 1

[0047] The present invention adopts electrochemical chlorination method, which has better controllability and the reference electrode prepared has better performance. The differences between the electrode of the present invention and the prior art are shown in Table 1:

[0048] Table 1 Differences between the electrode of the present invention and the prior art

[0049]

[0050] Comparative Example 2 Comparison of the effects of chemical chlorination and electrochemical chlorination on the performance of the reference electrode

[0051] To further verify the performance of the Fishbone-Ag / AgCl RE, open circuit potential (OCP) tests were performed to compare its stability and the appearance and shape of the Fishbone-Ag / AgCl RE prepared by chemical chlorination and electrochemical chlorination. The results showed that the performance of the Fishbone-Ag / AgCl RE prepared by electrochemical chlorination was superior to that of the Fishbone-Ag / AgCl RE prepared by chemical chlorination.

[0052] First, Fishbone-Ag / AgCl RE was prepared by chemical chlorination (the preparation conditions have been optimized, that is, 20 mg / mL NaClO solution was used for chlorination and the chlorination time was 60 s). The SEM image of the prepared Fishbone-Ag / AgCl RE is shown in Figure 2. Figure 1 Then, Fishbone-Ag / AgCl RE was prepared by electrochemical chlorination (using the optimal preparation conditions, namely, Ag deposition time of 1800s, chlorination potential of OCP+200mV, and chlorination time of 2700s). The SEM image of the prepared Fishbone-Ag / AgCl RE is shown in FIG. Figure 2 As shown. Figure 1It can be seen that the surface of the Fishbone-Ag / AgCl RE prepared by chemical chlorination method shows fragmented clusters. This is because Ag reacts with NaClO to form a large number of AgCl particles. The violent reaction process causes the fishbone structure to break. Therefore, even if AgCl particles are formed on the surface, the broken parts still hinder the high-speed transmission and transfer of electrons, thereby affecting the conductivity of the electrode. Figure 2 It can be clearly observed that the Fishbone-Ag / AgCl RE prepared by electrochemical chlorination still maintains the fishbone structure, and these nanoparticles are arranged in an orderly fishbone shape.

[0053] Figure 3 The OCP results for Fishbone-Ag / AgCl RE prepared by electrochemical chlorination and chemical chlorination in 3M KCl solution are shown. The experimental results show that the OCP of the Fishbone-Ag / AgCl RE prepared by electrochemical chlorination is more stable, while the potential of the Fishbone-Ag / AgCl RE prepared by chemical chlorination exhibits significant fluctuations. This indicates that the stability of the reference electrode prepared by electrochemical chlorination is far superior to that of the reference electrode prepared by chemical chlorination. This may be because the electrochemical chlorination method only forms AgCl particles on the surface of the Fishbone silver wire structure, leaving the structure of the Fishbone silver wire intact, allowing electrons to still transmit at high speed within the silver wire layer.

[0054] Comparative Example 3 Performance Comparison of Fishbone-Shaped RE and NWs-Shaped RE

[0055] The performance of the NWs-shaped reference electrode was compared with that of the fishbone-shaped reference electrode. The OCP test of Fishbone-Ag / AgCl RE was performed compared with that of AgNWs-Ag / AgCl RE. The results are as follows: Figure 4 As shown in Figure 2, the OCP curve of the Fishbone-Ag / AgCl RE exhibits less fluctuation than that of the AgNWs-Ag / AgCl RE, indicating that the Fishbone-Ag / AgCl RE possesses superior stability compared to the AgNWs-Ag / AgCl RE. This is likely due to the larger diameter of the Fishbone-like AgNWs structure, which allows chlorination to occur only on the surface of the nanostructure and not damage the inner silver layer. Therefore, the electron transfer rate of the electrode remains unaffected after chlorination. However, the smaller diameter of the AgNWs may have damaged the inner Ag layer of some of the silver wires, leading to instability in the electron transfer rate and the significant fluctuations seen in the OCP test.

[0056] Comparative Example 4: Stability comparison between Fishbone-Ag / AgCl RE and commercial hard glass Ag / AgCl RE

[0057] The OCP test was performed on the two reference electrodes mentioned above, and the results were as follows: Figure 5 As shown, the test curves of the Fishbone-Ag / AgCl RE and the commercial hard glass Ag / AgCl RE are both very stable, with little difference. This shows that the stability of the flexible reference electrode prepared by the present invention can reach the level of commercial hard glass Ag / AgCl RE, while the stability of the sheet reference electrode in the prior art cannot reach the level of commercial hard glass Ag / AgCl RE.

[0058] Furthermore, the stability of Fishbone-Ag / AgCl RE was studied after 3 days, 60 days, 120 days and 180 days of storage in a dark environment without N2 protection. Figure 6 As shown in the figure, the properties of Fishbone-Ag / AgCl RE remain very stable after 60 days of storage (ΔE<0.002V), and ΔE increases slightly after 120 and 180 days (ΔE<0.005V and ΔE<0.008V). The slight increase in ΔE does not affect the normal use of the electrode, which indicates that Fishbone-Ag / AgCl RE has a long storage period and outstanding operational stability.

[0059] Application Example 1: Application of Fishbone-Ag / AgCl RE in the Catalysis of Ethanol

[0060] Figure 7 The figure shows the comparison of the peaks of ethanol oxidation catalyzed by Fishbone-Ag / AgCl RE and commercial hard glass Ag / AgCl RE. Cyclic voltammetry was used to catalyze the oxidation of ethanol using PdNPs / AgNWs electrode as the working electrode, platinum wire electrode as the counter electrode, homemade Fishbone-Ag / AgCl and commercial hard glass Ag / AgCl as the reference electrodes. The experimental results are shown in Figure 2. Figure 7 As shown. Figure 7 It can be seen that the oxidation peak of ethanol in the homemade Fishbone-Ag / AgCl RE is similar to the oxidation peak of commercial hard glass Ag / AgCl RE, which shows that the Fishbone-Ag / AgCl RE prepared in the present invention can be used in the field of electrocatalysis.

[0061] Application Example 2: Applying Fishbone-Ag / AgCl RE to a small flexible electrochemical device for glucose detection

[0062] Fishbone-Ag / AgCl RE is easy to integrate, Figure 8This is a physical picture of the working electrode (PdNPs / AgNWs electrode), reference electrode (homemade Fishbone-Ag / AgCl electrode), and counter electrode (platinum electrode) integrated into the same device. The device was used for electrocatalysis of 20mM glucose, and the resulting cyclic voltammetry curve is shown in Figure 2. Figure 9 As shown in the figure, the oxidation peak of glucose appears at 0.1 V. It can be seen that Fishbone-Ag / AgCl RE can be used in small flexible electrochemical devices for glucose detection. This sheet reference electrode provides a possibility for the miniaturization and portability of electrochemical systems.

[0063] The above embodiments are merely examples and illustrations of the present invention and are not intended to limit the present invention to the scope of the described embodiments. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the above embodiments and that various variations and modifications may be made based on the teachings of the present invention, all of which fall within the scope of protection claimed by the present invention.

[0064] References

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[0066] [2]Zai JZ,Fu YB,Zai XR,Ji HW,LiuA,Chai F G.Fabrication ofnovelAg / AgCl electrodepair on the template of carbon foam as marine electric fieldsensor and its electrochemical performances[J].Ionics,2017,23(8):2213.

[0067] [3]Lindner E, Guzinski M, Khan TA, et al. Reference electrodes with ionic liquid salt bridge: when will these innovative novel reference electrodes gain broad acceptance[J]. Acs Sensors, 2019, 4(3):549-561.

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Claims

1. A method for preparing a reference electrode in a small flexible electrochemical device, characterized in that: The specific steps are as follows: Step 1: Prepare thermoplastic elastomer Flexdym material as a flexible substrate; Step 2: Soaking the Flexdym flexible substrate material in a modification solution for surface hydrophilic modification, wherein the modification solution is a mixed solution of 1-5% by mass polyacrylic acid and 5-10% by mass glycerol; Step 3: Preparation of fishbone-shaped Ag / AgCl reference electrode; Step 3.1: Evenly coat the AgNWs solution on the surface of the Flexdym substrate to obtain an AgNWs electrode; Step 3.2: The AgNWs electrode prepared in step 3.1 is placed in a mixed solution of AgNO3 and KNO3, and silver is deposited by chronopotentiometry to obtain a fishbone-shaped Ag electrode, wherein the concentration of the AgNO3 solution is 0.01-0.02M, the concentration of the KNO3 solution is 0.1-0.2M, and the silver is deposited by chronopotentiometry with a deposition current of -0.6 mA and a deposition time of 500-2000 s. Step 3.3: Chlorination of the fishbone-shaped Ag electrode: Using the fishbone-shaped Ag electrode prepared in step 3.2 as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum electrode as the counter electrode, electrochemical chlorination was performed in HCl solution using chronopotentiometry to obtain a fishbone-shaped Ag / AgCl reference electrode.

2. The method according to claim 1, characterized in that In step 3.1, the concentration of the AgNWs solution ranged from 1 to 5 mg / mL.

3. The method according to claim 1, characterized in that In step 3.3, electrochemical chlorination is performed using chronopotentiometry, the concentration of the HCl solution is 0.05-0.15 M, the chlorination potential is OCP+100 mV, OCP+150 mV, OCP+200 mV, OCP+250 mV or OCP+300 mV, and the chlorination time is 800 s, 1600 s, 2400 s, 2700 s or 3200 s.

4. The method according to claim 1, wherein In step 3.3, electrochemical chlorination was performed using chronopotentiometry, the concentration of the HCl solution was 0.1 M, the chlorination potential was OCP + 200 mV, and the chlorination time was 2700 s.

5. Use of the fishbone-shaped Ag / AgCl reference electrode prepared by the method described in claim 1 in the electrochemical catalysis and detection of ethanol.

6. Use of the fishbone-shaped Ag / AgCl reference electrode prepared by the method of claim 1 in a small flexible electrochemical device.

7. The use according to claim 6, wherein the fishbone-shaped Ag / AgCl reference electrode is used for glucose detection in a small flexible electrochemical device.

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